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uk Health & medical scares newborn fever • baby under 3 months fever • infant temperature 38c • baby feels hot under 12 weeks • baby unusually sleepy • hard to wake newborn • very sleepy baby not waking • lethargic baby under 3 months • newborn not feeding and sleepy • baby floppy or limp • newborn unwell sudden • fever in young infant • baby not themselves under 3 months • infant drowsy and warm • under 90 days fever • fever after vaccinations baby • worried newborn fever • under 8 weeks very worried

What to do if…
an infant under three months has a fever or feels unusually sleepy

Short answer

Treat this as urgent. If your baby is under 3 months and has a temperature of 38°C or higher (or you strongly suspect a fever), call NHS 111 or your GP urgently—and if they will not wake up normally, are very floppy, or breathing is a struggle, call 999 or go to A&E now.

Do not do these things

  • Do not “wait it out” because the fever seems mild—under 3 months needs urgent advice.
  • Do not rely on touch alone to decide it’s safe; check a temperature if you can.
  • Do not cool them with cold baths, ice packs, or rubbing alcohol.
  • Do not overdress or tightly wrap them.
  • Do not give paracetamol to a baby under 2 months unless a clinician tells you to.
  • Do not give ibuprofen to a baby under 3 months unless a doctor has prescribed/advised it.
  • Do not give aspirin.
  • Do not drive yourself if you feel you cannot stay calm or your baby seems to be getting worse quickly—use 999.

What to do now

  1. Get to a calmer pause (30–60 seconds). Put your baby on a firm, flat surface (or hold them securely) so you can watch breathing and responsiveness.
  2. If any of these are happening, treat it as an emergency: call 999 or go to A&E now.
    • They will not wake up normally, are very floppy/limp, or are not responding in their usual way
    • Breathing looks like hard work (grunting, very fast breathing, long pauses, chest “sucking in”)
    • Skin/lips look blue, very pale, mottled, or they feel unusually cold as well as unwell
    • A spotty purple/red rash that does not fade when you press the side of a clear glass against it
    • A seizure/fit, or you are seriously alarmed by how different they seem
    • They are under 8 weeks and you are very worried
  3. Check a temperature if you can (but don’t delay emergency help if they look very unwell).
    • Use a digital thermometer in the armpit.
    • Note the number and the time you took it.
  4. If the temperature is 38°C or higher, or you strongly suspect a fever: call NHS 111 or your GP urgently.
    • Start with: “Baby under 3 months … temperature 38 or above / unusually sleepy.”
    • Follow the advice you’re given (they may send you to an urgent assessment service or A&E).
  5. If the main worry is “unusually sleepy,” treat that as urgent even without a confirmed temperature.
    • If they are too sleepy to feed normally, much harder to wake than usual, or “not themselves,” call NHS 111/GP urgently; if they won’t wake, use 999/A&E.
  6. While you’re getting help, do simple supportive steps:
    • Keep them lightly dressed (one layer more than you).
    • Offer feeds as normal; if breastfed, offer more frequently. Don’t force.
    • Note wet nappies today (fewer than usual can matter), and any vomiting/rash/breathing changes.
  7. Write down 6 quick facts (takes 1 minute) to tell the clinician:
    • Age in weeks, highest temperature and when, how alert they are,
    • Feeding amount/frequency, wet nappies today,
    • Any rash/breathing changes/vomiting,
    • Any recent vaccinations (and when),
    • Any medicines already given (name/time).
  8. Be ready to leave if asked.
    • Take the red book, a spare nappy, wipes, a blanket, and your notes.

What can wait

  • You do not need to work out the cause right now.
  • You do not need to try “cooling tricks” (sponging/cold baths/over-undressing).
  • You do not need to decide about tests or treatment—focus on urgent clinical assessment.
  • If the fever started soon after routine vaccinations, that can happen—still get urgent advice if your baby is under 3 months and you’re worried or they seem unwell.

Important reassurance

It’s normal to feel frightened when a very young baby seems hot or unusually sleepy. Acting quickly here is the right kind of caution—clinicians would rather assess early.

Scope note

These are first steps only: urgent safety checks, taking a temperature, and getting the right UK help fast.

Important note

This is general information, not a diagnosis. If your baby seems to be getting worse, is hard to wake, or is having trouble breathing, seek urgent medical help immediately.

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